The present invention relates to an oil system for an aircraft gas turbine engine, and relates in particular to an oil system which provides an uninterrupted supply of oil to the engine bearing chambers during any aerobatic maneuvers of the aircraft.
Many proposals have been made to avoid the problems associated with oil starvation in the bearing chambers when, for example, an aircraft takes up an inverted attitude, and the oil in the oil tank falls away from the pump inlet preventing the pump from supplying any oil. As a result, in addition to the possibility of bearing failure, the cooling effect of the oil is removed so that the walls of the chamber heat up, increasing the risk of an oil fire when normal oil flow is restored.
The proposals have usually centred around the provision within the tank of baffles to maintain a reservoir of oil at the pump inlet during inverted flight, and the positioning of the pump inlet within the reservoir so that the pump continues to supply oil for a limited period.
These solutions have enabled limited aerobatic maneuvers to be performed but have not enabled aircraft to remain in attitudes other than normal level flight, or to sustain zero or high "g" maneuvers for significant lengths of time.